GILENYA may cause serious side effects such as:•;Slow;heart;rate,;especially;after;your;first;dose.;An;ECG;will;beperformed;before;and;6;hours;after;your;first;dose.;Your;pulseand;blood;pressure;should;be;checked;every;hour;while;youstay;in;a;medical;facility;during;this;time.;If;your;heart;rateslows;down;too;much,;you;might;feel;dizzy;or;tired,;or;feel;likeyour;heart;is;beating;slowly;or;skipping;beats.;Symptoms;canhappen;up;to;24;hours;after;your;first;dose.;After;6;hours,;ifyour;ECG;shows;any;heart;problems;or;if;your;heart;rate;is;stilltoo;low;or;continues;to;decrease,;you;will;continue;to;bewatched;by;a;health;care;professional.;If;you;have;any;seriousside;effects;after;your;first;dose,;especially;those;that;requiretreatment;with;other;medicines,;you;will;stay;in;a;medicalfacility;to;be;watched;overnight;and;for;at;least;6;hours;afteryour;second;dose;of;GILEN YA;the;next;day.;If;you;have;certaintypes;of;heart;problems,;or;if;you;are;taking;certain;types;ofmedicines;that;can;affect;your;heart,;you;will;be;watchedovernight;after;you;take;your;first;dose.;If;you;experience;slowheart;rate,;it;will;usually;return;to;normal;within;1;month.;Callyour;doctor;or;go;to;the;nearest;emergency;room;right;away;ifyou;have;any;symptoms;of;a;slow;heart;rate.;If;you;stop;takingGILENYA;for;more;than;14;days;after;your;first;month;oftreatment,;you;will;need;to;repeat;this;observation.